1. Field of the Invention
Embodiments relate to a flash memory device and, more particularly, to a flash memory device having a verify data buffer which, in addition to being employed as a verify data buffer, may be employed as a program data buffer, and a method thereof.
2. Description of the Related Art
In general, flash memory devices are an integrated nonvolatile memory that may be electrically erased and programmed. Typical flash memory devices may have the advantages of RAM, which may allow data to be stored or accessed in any order, and the advantages of ROM, which may retain stored data when power is not supplied. Due at least in part to these advantages, flash memory devices are widely used as storage mediums of portable electronic devices such as digital cameras, personal digital assistants (PDAs), and MP3 players.
A single-level cell (SLC) flash memory may store one bit of data in one memory cell. On the contrary, a multi-level cell (MLC) flash memory may store two bits of data in one memory cell in order to increase the degree of integration.
One-bit data may be stored in a memory cell as two different programmed threshold voltages in the case of the single-level cell. As one example, if the threshold voltage programmed in a memory cell is about 1 to 3 volts, the data stored in the memory cell may represent logic 1. If the threshold voltage programmed in the memory cell is about 5 to 7 volts, the data stored in the memory cell may represent logic 0.
Two-bit data may be stored in a memory cell as four different programmed threshold voltages in the multi-level cell. As one example, if the threshold voltage programmed in a memory cell is about 1 to 3 volts, the data stored in the memory cell may represent logic 11. If the threshold voltage programmed in the memory cell is about 3.8 to 4.2 volts, the data stored in the memory cell may denote logic 10. If the threshold voltage programmed in the memory cell is about 4.9 to 5.4 volts, the data stored in the memory cell may represent logic 01. If the threshold voltage programmed in the memory cell is about 6.5 to 7.0 volts, the data stored in the memory cell may denote logic 00.
A flash memory cell device having a single-level cell or a multi-level cell may distinguish data stored in a memory cell based on the difference of cell current when a read operation is performed. Because the operations of the SLC flash memory device and the MLC flash memory are well-known to those skilled in the art, a detailed description thereof is omitted.
As described above, one cell may have two states in the SLC flash memory device, and one cell may have four states in the MLC flash memory device. Therefore, the MLC flash memory device may require a program and verify method that may have an increased accuracy as compared with the SLC flash memory device.